Process for the epoxidation of an olefin
In a process for the epoxidation of an olefin, where a mixture comprising olefin, hydrogen peroxide, water and methanol with a weight ratio of water to methanol of less than 1 is passed through a catalyst fixed bed comprising a shaped titanium silicalite catalyst, catalyst breakage is reduced by conditioning the dry catalyst with at least one conditioning liquid comprising water and from 25 to 45% by weight methanol.
1. A process for the epoxidation of an olefin, comprising the steps:
a) providing a dry, shaped titanium silicalite catalyst;
b) contacting said catalyst with a first conditioning liquid comprising more than 60% by weight water and less than 40% by weight methanol to provide a conditioned catalyst;
c) optionally contacting said catalyst subsequent to step b) with at least one further conditioning liquid having a methanol content higher than the methanol content of said first conditioning liquid; and
d) passing a mixture comprising olefin, hydrogen peroxide, water and methanol through a catalyst fixed bed comprising said conditioned catalyst, wherein the weight ratio of water to methanol is less than 1;
wherein at least one of said conditioning liquids comprises water and from 25 to 45% by weight methanol with the combined amount of water and methanol being at least 95% by weight.
2. The process of claim 1 , wherein in step a) the dry, shaped titanium silicalite catalyst is provided in said fixed bed.
3. The process of claim 2 , wherein in step b) said first conditioning liquid is passed through said catalyst fixed bed.
4. The process of claim 2 , wherein in step c) said further conditioning liquid is passed through said catalyst fixed bed.
5. The process of claim 4 , wherein further conditioning liquid is passed through said catalyst fixed bed and the methanol content of said further conditioning liquid is increased to more than 50% by weight, starting from the methanol content of said first conditioning liquid, and this increase is continuous or is stepwise in steps changing the methanol content by no more than 25% by weight at a time.
6. The process of claim 5 , wherein the methanol content of said further conditioning liquid is increased at an average change rate in % by weight per hour that is 1 to 50 times the ratio of the volume flow rate of further conditioning liquid passed through said catalyst fixed bed to the volume of said catalyst fixed bed.
7. The process of claim 1 , wherein in step b) said first conditioning liquid comprises at least 75% by weight water and no more than 25% by weight methanol.
8. The process of claim 1 , wherein in steps b) and c) the temperature of said conditioning liquid is maintained in the range of from 0 to 100° C.
9. The process of claim 2 , wherein said catalyst fixed bed is cooled in steps b) and c).
10. The process of claim 1 , wherein in steps b) and c) the pressure is in the range of from 0.1 to 5 MPa.
11. The process of claim 1 , wherein said shaped titanium silicalite catalyst is in the form of extrudates.
12. The process of claim 11 , wherein said extrudates have a cylindrical shape with a diameter of from 2 to 5 mm and a length of from 2 to 7 mm.
13. The process of claim 11 , wherein said extrudates comprise a silica binder.
14. The process of claim 1 , wherein in step d) the weight ratio of water to methanol is less than 0.25.
15. The process of claim 1 , wherein in step d) said olefin is propene.
16. The process of claim 7 , wherein in step a) the dry, shaped titanium silicalite catalyst is provided in said fixed bed.
17. The process of claim 16 , wherein in step b) said first conditioning liquid is passed through said catalyst fixed bed.
18. The process of claim 16 , wherein in step c) said further conditioning liquid is passed through said catalyst fixed bed.
19. The process of claim 18 , wherein further conditioning liquid is passed through said catalyst fixed bed and the methanol content of said further conditioning liquid is increased to more than 50% by weight, starting from the methanol content of said first conditioning liquid, and this increase is continuous or is stepwise in steps changing the methanol content by no more than 25% by weight at a time.
20. The process of claim 19 , wherein the methanol content of said further conditioning liquid is increased at an average change rate in % by weight per hour that is 1 to 50 times the ratio of the volume flow rate of further conditioning liquid passed through said catalyst fixed bed to the volume of said catalyst fixed bed.